The present invention is directed generally to apparatus for controlling fuel input into a spark ignited and direct injection internal combustion engine. More specifically, the present invention is directed to fuel injector apparatus having a component such as a nozzle and/or plunger manufactured from an iron aluminide alloy or having at least a portion of a fuel contacting surface coated with an iron aluminide alloy.
Internal combustion engines operate by combusting fuel supplied to one or more combustion chambers. It is conventional to use one or more fuel injectors to supply fuel to an individual combustion chamber. See, for example, U.S. Pat. Nos. 4,458,655; 4,886,032; 5,331,937; 5,482,023; 6,067,970; and 6,155,212. Of these, the ""655 patent states that the fuel injector is made of steel and other components such as the spray tip body, spray tip, bushing, valve, coil spring, spacer ring, cap, adjusting screw are made of an electrically conductive material such as steel. The ""212 patent discloses use of catalytic coatings such as platinum, palladium, osmium, iridium, nickel, nickel oxide and intermetallics of transition metals such as vanadium-copper-zinc on the surface of valve seats of an electrode spray nozzle. To improve cold starting capabilities, some fuel injectors deliver heated fuel to the combustion chamber. See, for example, U.S. Pat. No. 5,758,826. Some fuel injectors can incorporate an integral fuel pump and/or sensor arrangement. See, for example, U.S. Pat. Nos. 5,716,001 and 6,283,095.
Fuel injectors have been proposed for direct injection engines. See, for example, U.S. Pat. Nos. 6,116,218; 6,267,307; and 6,295,969. Of these, the ""307 patent states that a high-performance ceramic coating can be deposited on injector tips made from a nickel and chrome alloy. According to the ""969 patent, direct injection can be used for two-cycle or four-cycle engines such as outboard motors or other engines for marine propulsion or land vehicles or utility machines such as lawn mowers.
Conventional fuel injectors can include a housing having an internal passage and the injector can be installed in a fuel rail to supply the passage with fuel under pressure. A solenoid operated needle valve can be moved on and off a valve seat to control the outflow of fuel from the injector from the injector nozzle or tip. The injector nozzle can be received in a bore in an intake manifold or cylinder head runner passage of a spark ignited and direct injection internal combustion engine. With such an arrangement, fuel can be injected in the form of a spray as an aid to vaporization of the fuel.
Fuel injectors can be designed to operate with a given fuel volumetric flow rate and a fuel spray pattern for optimization of fuel economy and reduction in exhaust emissions. A recognized problem in fuel injection is the formation of coke that can foul the injector nozzle. Coking is a surface phenomenon which has bee observed with iron and nickel-based alloys containing chromium in the range of 10 to 25 wt. %. In addition to negatively impacting thermal performance, coking can result in an excessive pressure drop across the injector nozzle, even blocking of the injector nozzle, thereby adversely affecting the fuel injector and the engine performance. For example, carbon deposits may alter the spray pattern such that the spray penetrates to an undesirable depth in the combustion chamber. Poor atomization can also lead to higher levels of exhaust particles and increase levels of soot in the crank case. Further, coking can lead to increased pressure in the fuel injector, and the degradation of mechanical properties can lead to catastrophic failure of injector nozzles and is a safety hazard.
Another problem in fuel injector nozzles is carburization (e.g., carburization can be severe with alloys such as HP steels, INCO 803, and other materials that contain significant amounts of chromium and nickel). Carburization results in the formation of carbides in the metal matrix or in grain boundaries of metallic components from exposure to a carbon containing atmosphere.
A variety of solutions have been proposed for addressing the problems of coke formation, carburization, and related materials phenomena in fuel injector nozzles. See for example, U.S. Pat. No. 6,267,307 B1 to Pontoppidan, A. A. Aradi, et al., xe2x80x9cThe Effect of Fuel Composition and Engine Operating Parameters on Injector Deposits in a High-Pressure Direct Injection Gasoline (DIG) Research Enginexe2x80x9d, SAE Technical Paper Series, 1999-01-3690 (1999), and S. Rossi et al., xe2x80x9cCorrosion Behavior of P/M Components for Gasoline Injectorsxe2x80x9d, International Journal of Powder Metallurgy, Vol. 36, pp. 39-46 (2000).
U.S. Pat. No. 3,582,323 discloses iron-aluminum alloys having 30 to 50 atomic % aluminum and up to 6 atomic % hardening elements(Zr, Mo, C, Ti, V, Ta, La) for exhaust valves of internal combustion engines. U.S. Pat. Nos. 5,328,527 and 5,425,821 disclose an iron aluminum alloy having 9 to 13.3 weight % Al, 0.05 to 0.35% C, 0.5 to 3% refractory metal (V, Mo, Nb, W, Ta) and/or 0.3 to 1.5% Ti for an intake valve of an internal combustion engine. U.S. Pat. No. 6,085,714 states that titanium aluminide has been proposed as a replacement for steel inlet and exhaust valves.
Commonly owned U.S. Pat. No. 5,620,651 discloses aluminum containing iron base alloys useful as coatings having oxidation and corrosion resistance or as sulfidization or corrosion resistant materials for use in the chemical industry, pipe for conveying coal slurry or coal tar, substrate materials for catalytic converters, exhaust pipes for automotive engines or porous filters. According to U.S. Pat. No. 3,026,197, iron base alloys having 10 to 18 weight % aluminum can be alloyed with Zr and B to refine the grain structure and thus enhance workability of the otherwise brittle alloys.
Thus it would be advantageous to limit the deposition of carbon and carbon by-products on the interior surfaces of components of fuel injectors and to inhibit the carburization of system metallurgical components. Additionally, it would be advantageous that the fuel injector material exhibit strength at operating temperatures and oxidation resistance. Thus, there is a need in the art for fuel injector materials with improved materials performance that address these needs and others.
The invention provides a component of a fuel injector such as an injector nozzle or plunger wherein the component comprises a coating or bulk part of an iron aluminide alloy. The injector nozzle can have any desired configuration. For example, the injector nozzle can include a recess in a first surface adapted to engage a plunger of the fuel injector. Alternatively, the injector nozzle can include a body formed from a first material and having a recess in a first surface adapted to engage a plunger of the fuel injector, and a coating of a second material disposed on at least a portion of the recess wherein the second material is an iron aluminide alloy. In a preferred embodiment, the recess is substantially in the form of an inverted frustum of a right circular cone.
The iron aluminide alloy can be cast and thermomechanically processed into the shape of the component or the component can be made by sintering an iron aluminide alloy powder. The iron aluminide alloy preferably has at least 8 wt. % aluminum and optional alloying additions such as up to 5 wt. % of one or more refractory metals (e.g., Ti, Ta, Nb, W, Cr, Mo, V, Hf and Zr), up to 0.02 wt. % B, up to 0.5 wt. % C, up to 1% rare earth metal (e.g., Y, La, etc.). For example, the iron aluminide can further comprise B and/or C in an amount effective to provide borides and/or carbides in the iron aluminide alloy. If desired, up to 20 vol. % oxide particles can be incorporated in the iron aluminide (e.g., Al2O3, Y2O3, etc.). An exemplary iron aluminide can include 10-32 wt. % Al, up to 20 vol. % transition metal oxides, up to 0.020 wt. % B, up to 2.0 wt. % Mo, up to 1.0 wt. % Zr, up to 2.0 wt. % Ti, up to 1.0 wt. % La, up to 0.2 wt. % C, up to 1 wt. % Cr, balance Fe and impurities.
A method of manufacturing a fuel injector component such as an injector nozzle includes hot extruding a cast iron aluminide material and machining the extruded body or pressing an iron aluminide powder into a shape and sintering the shape to a density of at least 90% theoretical density. For example, the iron aluminide can be a sintered nanocrystalline iron aluminide powder. If desired, the fuel injector component can be formed by forming iron aluminide powder into a body and sintering the body to a density of at least 90% theoretical density.
In an embodiment in which the fuel injector component has a coating of an iron aluminide alloy, the component is made by forming a first material into the shape of the component and coating an iron aluminide alloy on at least a portion of a surface of the first material that directly contacts fuel during operation. The coating can be formed by various techniques including a diffusion reaction process or a cathodic plasma process.
The fuel injector component can be provided with various properties such as corrosion, carburization, sulfidation and/or coking resistance and a fuel injector with such a component can be operated in a manner which produces reduced greenhouse emissions and reduced particulate matter.